Epidemiology
The disease is found in two forms, depending on the parasite, either Trypanosoma brucei gambiense or Trypanosoma brucei rhodesiense. Humans are the main reservoir for T. b. gambiense, but this species can also be found in pigs and other animals. Wild game animals and cattle are the main reservoir of T. b. rhodesiense. T. b. gambiense is found in central and western Africa; it causes a chronic condition that can remain in a passive phase for months or years before symptoms emerge. T. b. rhodesiense is the acute form of the disease, but has a much more limited geographic range, being found in southern and eastern Africa. Symptoms of infection emerge in a few weeks; it is more virulent and faster developing than T. b. gambiense. According to recent estimates, the disability-adjusted life-years (9 to 10 years) lost due to sleeping sickness are 2.0 million. Recent estimates indicate over 60 million people living in some 250 locations are at risk of contracting the disease, and under 10,000 new cases were reported in 2009 according to WHO figures, which represents a huge decrease from the estimated 300,000 new cases in 1998. The disease has been recorded as occurring in 36 countries, all in sub-Saharan Africa. It is endemic in southeast Uganda and western Kenya, and killed more than 48,000 Africans in 2008.
Horse-flies (Tabanidae) and stable flies (Muscidae) possibly play a role in transmission of nagana (the animal form of sleeping sickness) and the human disease form.
Read more about this topic: African Trypanosomiasis